[PDFBOX-4276] Multiply blend mode not detected

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.8.15, 2.0.11, 3.0.0 PDFBox
• Fix Version/s: 1.8.16, 2.0.12, 3.0.0 PDFBox
• Component/s: Preflight
• External issue URL: https://bugs.ghostscript.com/show_bug.cgi?id=699554
• Assignee: Tilman Hausherr
• Reporter: Tilman Hausherr
• Created: 24/Jul/18 16:53
• Updated: 05/Oct/18 04:53
• Resolved: 24/Jul/18 17:03

Description

The attached file should fail the PDF/A-1b check but doesn't. VeraPDF detects the incorrect blendmode at Root/Pages/Kids/[0]/Resources/ExtGState/R9/BM: "The following keys, if present in an ExtGState object, shall have the values shown: BM - Normal or Compatible".

The cause is that in ExtGStateValidationProcess.extractExtGStateDictionaries() there is a check that the name of the ExtGState matches "(GS|gs)([0-9])+". This has been since the beginning as an Apache project (PDFBOX-1056) and even since the first commit on github (https://github.com/gbm-bailleul/padaf) in 2010.

I could ask but I don't think that they would know why that decision was made over 8 years ago. My guess is that some code from elsewhere was reused.